This invention relates to the art of onboard systems for inflating and deflating the tires of a wheeled vehicle and, more particularly, to an improved tire isolating valve for use in such a system to maintain a desired tire pressure following an inflation or deflation operation.
It is well known in the art to provide vehicles with onboard systems for achieving inflating and deflating of vehicle tires in order to optimize operation of the vehicle under variable and changing conditions including, for example, weather, vehicle load, terrain and vehicle speed. Such systems generally include a source of air under pressure on the vehicle and manually operable controls for selectively inflating or deflating the vehicle tires to respectively increase or decrease an existing tire pressure. Such systems further include a wheel valve or tire isolating valve which is operable to maintain air under pressure in each vehicle tire independently of the other tires so that a problem such as a leak in one tire does not affect the air pressure in the other tires. In connection with such a tire isolating feature, it is generally the practice to connect the source of air under pressure on the vehicle to each wheel assembly of the vehicle through passages drilled in the fixed axle upon which the wheel assembly is rotatably mounted or passages drilled in the hub which is rotatable relative to the axle and which carries the tire. In either instance a sealing arrangement is required between the fixed and rotating parts to preclude the leakage of air therebetween. The tire isolating valve is preferably between the sealing arrangement and the tire or tires of the wheel assembly so that the sealing arrangement is not subjected to system air under pressure other than at times of operation of the system to achieve inflation or deflation. While such prior arrangements provide a sealed air flow path between the onboard air supply and the tires of a vehicle, they are structurally complex and expensive and, often, require special seal designs and/or special designs or major modifications of otherwise standard vehicle axle, hub and/or bearing components to accommodate the air flow passages and seal assemblies. Such designs and modifications often result in component parts which are limited in use to a given wheel and axle assembly design for a given onboard tire inflating and deflating system. Furthermore, such special modifications or design can effect the structural integrity of component parts of the wheel and axle assembly and do not lend to the efficient and economical retrofitting of a vehicle to provide the latter with an onboard tire inflating and deflating system. Arrangements of the foregoing character including bored passageways through a fixed axle or the hub of the wheel assembly together with sealing arrangements between the axle and hub are shown for example in U.S. Pat. No. 2,976,906 to Kamm et al and in my U.S. Pat. No. 4,892,128.
It has also been proposed as shown in U.S. Pat. No. 2,685,906 to Williams to provide a tire isolating valve in the form of relatively rotatable valve parts, one of which is mounted on the hub of a vehicle wheel for rotation therewith and provided with a conduit for connecting the valve to the corresponding tire. The other valve part has a conduit for connecting the valve to the source of air under pressure on the vehicle and includes a pneumatically actuated piston for displacing a conventional tire valve element of the valve unit between open and closed positions to achieve tire inflating and deflating. While an arrangement such as that shown in Williams avoids having to bore air passageways in the axle and/or hub components of a vehicle wheel assembly, the valve is structurally complex and expensive, requires an excessive amount of axial space relative to the hub to accommodate the component parts thereof and, in particular, actuating displacement of the movable parts thereof. Moreover, the valve includes both valve and seal components which are exposed to excessive wearing interengagement during operation of the valve .with the vehicle in motion. Moreover, the pneumatically actuated piston by which the valve is operated is in the axially outer part of the valve relative to the vehicle wheel and, thus, is more exposed to potential damage than are the component parts which are in the valve part attached to the wheel hub. Still further, insofar as individual tire pressure is concerned, the valve is not capable of inflating or deflating dual tires on a common hub assembly on one end of a vehicle axle.